added __version__ attribute to brownie for issue #1575

[ryanjsfx2424]

What I did

Added a version attribute to brownie.

Related issue: #1575

How I did it

Imported version from _config.py in init.py

How to verify it

(yt-fork-env) ryanjsfx@MB-145 brownie-ryanjsfx % python3
Python 3.8.9 (default, Jul 19 2021, 09:37:30)
[Clang 13.0.0 (clang-1300.0.27.3)] on darwin
Type "help", "copyright", "credits" or "license" for more information.

import brownie
brownie.version != None
True

Checklist

• I have confirmed that my PR passes all linting checks
• I have included test cases
• I have updated the documentation
• I have added an entry to the changelog

Not that it fails tox -e lint due to:

brownie/__init__.py:7:1: F401 'brownie._config.__version__' imported but unused
ERROR: InvocationError for command /Users/ryanjsfx/Documents/brownie-ryanjsfx/.tox/lint/bin/flake8 brownie tests (exited with code 1)

```___________________________________ summary ____________________________________
ERROR:   lint: commands failed

Although it's not supposed to be used...¯\_(ツ)_/¯

I prob need to include a test case and update docs but in case you all don't want this included (or tackled from a different angle) I thought I should just submit the PR now :)

[chanhosuh]

Although it's not supposed to be used...¯_(ツ)_/¯

You need to add it to __all__.